The present invention is related to a railway car having a composite box structure mounted on a railway car underframe and more particularly to a roof assembly and airflow management system for a temperature controlled railway car.
Over the years, general purpose railway box cars have progressed from relatively simple wooden structures mounted on flat cars to more elaborate arrangements including insulated walls and custom designed refrigeration equipment. Various types of insulated box cars are presently manufactured and used. A typical insulated box car includes an enclosed structure mounted on a railway car underframe. The enclosed structure generally includes a floor assembly, a pair of side walls, a pair of end walls and a roof. The side walls, end walls and roof often have an outer shell, one or more layers of insulation and interior paneling.
The outer shell of many railway box cars often has an exterior surface formed from various types of metal such as steel or aluminum. The interior paneling is often formed from wood and/or metal as desired for the specific application. For some applications the interior paneling has been formed from fiber reinforced plastic (FRP). Various types of sliding doors including plug type doors are generally provided on each side of conventional box cars for loading and unloading freight. Conventional box cars may be assembled from various pieces of wood, steel and/or sheets of composite materials such as fiberglass reinforced plastic. Significant amounts of raw material, labor and time are often required to complete the manufacture and assembly of conventional box cars.
The underframe for many box cars include a center sill with a pair of end sills and a pair of side sills arranged in a generally rectangular configuration corresponding approximately with dimensions for the floor of the box car. Cross bearers are provided to establish desired rigidity and strength for transmission of vertical loads to the associated side sills which in turn transmit the vertical loads to the associated body bolsters and for distributing horizontal end loads on the center sill to other portions of the underframe. Cross bearers and cross ties cooperate with each other to support a plurality of longitudinal stringers. The longitudinal stringers are often provided on each side of the center sill to support the floor of a box car. Examples of such railway car underframes are shown in U.S. Pat. Nos. 2,783,718 and 3,266,441.
Traditionally, refrigerated box cars often have less inside height than desired for many types of lading and a relatively short interior length. Heat transfer rates for conventional insulated box cars and refrigerated box cars are often much greater than desired. Therefore, refrigeration systems associated with such box cars must be relatively large to maintain desired temperatures while shipping perishable lading.
Ballistic resistant fabrics such as Bulitex scuff and wall liners are currently used to form liners for highway truck trailers.
A wide variety of composite materials have been used to form railway cars and particular box cars. U.S. Pat. No. 6,092,472 entitled xe2x80x9cComposite Box Structure For A Railway Carxe2x80x9d and U.S. Pat. No. 6,138,580 entitled xe2x80x9cTemperature Controlled Composite Box carxe2x80x9d show some examples. One example of a composite roof for a railway car is shown in U.S. Pat. No. 5,988,074 entitled xe2x80x9cComposite Roof for a Railway Carxe2x80x9d.
In accordance with teachings of the present invention, disadvantages and problems associated with insulated box cars, refrigerated box cars and other types of temperature controlled railway cars have been substantially reduced or eliminated. One embodiment of the present invention includes a roof assembly and an airflow management system satisfactory for use with a refrigerated box car or a temperature controlled railway car.
A roof assembly and airflow management system formed in accordance with teachings of the present invention provides a railway car with enhanced insulation, increased load carrying capacity, better temperature regulation, increased service life, and reduced maintenance costs as compared to a typical refrigerated box car. The roof assembly may be formed from vacuum molded, single pour, one piece, FRP panels or sheets. Various types of insulating materials and insulating foams may be encapsulated between two FRP panels or sheets. Vacuum infusion techniques may also be used to form portions of the roof assembly. Alternatively, a roof assembly may be formed from one or more pultrusions. Void spaces associated with such pultrusions are preferably filled with insulating foam.
Technical benefits of the present invention include flexible joints or flexible connections provided between a roof assembly and associated side wall assemblies and the end assemblies to allow expansion and contraction of these components in response to temperature changes while maintaining desired structural integrity of an associated composite box structure.
One aspect of the present invention includes an airflow management system defined in part by an air plenum attached to and extending from an interior surface of a roof assembly. The air plenum may direct air from a temperature control unit to selected portions of a composite box structure. The temperature control unit may be mounted on one of the end wall assemblies of the composite box structure. An interior bulkhead may be formed within the composite box structure adjacent to and spaced from the one end wall assembly to provide portions of an airflow path to return air to the temperature control unit.